The technical scope of the invention is that of devices providing protection for a vehicle wall against attack by a projectile.
Vehicles have seen their protective means develop over the years to enable them to better withstand a threat. The most conventional form of protection is constituted by passive armor made of metal or else of several layers of composite materials.
So-called reactive armor is also known comprising a layer of explosive placed between two metallic plates. The explosive of this armor is ignited by the impact of an incident projectile. The detonation of the explosive causes the metallic plate to be projected outwards towards the projectile, thereby destabilizing and/or destroying it. The latter type of armor is more particularly adapted to protection from shaped charges and fin-stabilized projectiles.
So as to make the protection even more effective, so-called active armor is currently being designed. This type of armor incorporates a threat attack module coupled with threat detection means, for example radar or infrared. When an incident projectile has been detected, the attack module is activated and projects a plate or metallic block or else splinters onto the incident projectile.
Patent EP922924 describes such an active armor that comprises a plurality of launchers allowing one or several metallic blocks to be projected onto a fin-stabilized projectile. Projection is ensured by explosive or else by a propellant charge. The projection rate is between 100 and 500 m/s.
The main drawback to this device lies in that the projected projectiles are cylindrical or parallelepipedic blocks having a relatively reduced ratio of their total length to their smallest crosswise dimension (of between around 1 and 5).
This results in a low incident projectile interception probability by the projected block. Such a device thus requires the use of very efficient detection means allowing the incident projectile to be located quickly and accurately.
Moreover, the projection rate for these blocks is relatively low thereby requiring the protection to be triggered at a reduced distance from the incident projectile, once again obliging the detection means to be very efficient.
Lengthening the blocks so as to make bars may be envisaged, however the problem is posed of projecting such bars when faced with a threat whilst reducing the strain on the bar as much as possible.
Indeed, if the bar is strained through the effect of the explosive when being projected, such a strain is not reproducible and this results in a reduction in the interception capabilities.
The aim of the invention is to propose a protection device that does not suffer from such drawbacks.
Thus, the protection device according to the invention is of improved effectiveness as it allows the probability of intercepting an incident projectile to be increased while ensuring the reproducibility of the performances.
Thus, the invention relates to a wall-protection device, notably for a vehicle wall, against attack by a projectile and comprising at least one explosive charge able to project at least one metallic block in the direction of the projectile, the device wherein the block or blocks are in the shape of elongated bars, that is, which have a maximal length greater than or equal to 10 times their smallest crosswise dimension, the explosive charge being position opposite a longitudinal surface of the bar. The bar can be parallelepipedic, for example with a rectangular cross-section.
According to an essential characteristic of the invention, the explosive charge can be ignited by priming means that will be placed at one end of the bar.
The device can incorporate a support having a bottom plate intended to be fastened to the wall and onto which the explosive charge is placed.
The support can incorporate a longitudinal cavity delimited by two lateral cheeks and accommodating the explosive charge and the bar or bars.
According to a particular embodiment, the device can incorporate at least two bars placed substantially in the prolongation of one another in the same support.
According to another embodiment, the device can incorporate at least two bars placed substantially in parallel to one another in the same support.
According to a variant, the device can incorporate three bars placed substantially in parallel to one another in the same support.
According to another variant, the device can incorporate at least one intermediate layer of a material having a specific sound impedance of the same magnitude as that of the bars, said intermediate layer being placed between the explosive charge and the bars. The intermediate layer can comprise a copper sheet of a thickness of 0.5 to 1 mm.
According to another embodiment, the support can be placed in a case. A layer of shock-absorbing material can be placed between the support and the case. The layer of shock-absorbing material can notably be placed between the case and the bottom and two lateral faces of the support. The shock-absorbing material comprises a material having a high volume compressibility modulus.
The shock-absorbing material will thus be selected from among the following materials: high densityxe2x80x94for example greater than 1.2 g/cm3xe2x80x94organic foam, composite material, glass-fiber reinforced polyester, or a granular material, such as sand, plaster, shot, vermiculite, or glass beads, the granular material coated or not by a binder.
According to a structural characteristic of the invention, the bar or bars can be held integral with the support or case by means of at least two end shims pressing on an external surface of the bar or bars and made integral with the support or case by attachment means.
According to another embodiment, the explosive charge can incorporate at least two layers of explosives having different detonation rates, the detonation rate of the explosive in contact with the support being greater than that of the other explosives.